As an input device, a touch screen is so far the easiest, most convenient and natural method for human-computer interaction. Display devices integrated with a touch-control function have been a research hotspot among growing flat panel display manufacturers.
FIG. 1 is a top view of a typical mutual capacitive display panel. As shown in FIG. 1, a display panel 10A comprises a plurality of scanning lines 122 extending along an X direction, a plurality of data lines 124 extending along a Y direction, a plurality of drive electrodes 101 arranged in an array along both X direction and Y direction, and a plurality of sense electrodes 103 arranged along the X direction. In particular, the drive electrodes 101 and the sense electrodes 103 are perpendicularly distributed. The drive electrodes 101 are connected to a control unit 108 via touch-control drive electrode lines 107, the sense electrodes 103 are connected to the control unit 108 via touch-control sense electrode lines 109, and the control unit 108 inputs a touch-control drive signal to the touch-control drive electrodes 101 via the touch-control drive electrode lines 107. When touched by a finger, the capacitance at each crossing position between the drive electrodes 101 and the sense electrodes 103 varies, and the capacitance change signal of the touch-control sense electrodes 103 is received via the touch-control sense electrode lines 109, so as to determine a touch position.
As shown in FIG. 1, the drive electrodes 101 and the sense electrode 103 are disposed on a same layer. To avoid a short circuit caused by overlapping of the drive electrodes 101 and the sense electrodes 103, the drive electrodes 101 disposed on a same line are connected to each other via metal bridges 105.
FIG. 2 is a top view of a typical current self-capacitive display panel. As shown in FIG. 2, a display panel 10B comprises a plurality of scanning lines 126 extending along the X direction, a plurality of data lines 128 extending along the Y direction, a plurality of touch-control block electrodes 104 arranged in an array both along the X direction and the Y direction, each touch-control block electrode 104 is connected to a control unit 110 via touch-control lines 106.
Different from the working principle of the mutual capacitive display panel 10A, the touch-control block electrodes 104 in the self-capacitive display panel 10B are both touch-control drive electrodes and touch-control sense electrodes, and the control unit 110 provides an input touch-control drive signal for the touch-control electrodes 104 via the touch-control electrode lines 106. When touched by a finger, the capacitance of the touch-control electrodes 104 changes, this kind of change can be detected via touch-control electrodes 104 in order to determine a touch position. As shown in FIG. 2, to avoid signal interference between the touch-control electrodes 104 and the touch-control electrode lines 106, the touch-control electrodes 104 and the touch-control electrode lines 106 are disposed on different film layers and are connected via through-holes 108.
Neither the mutual capacitive display panel shown in FIG. 1 nor the self-capacitive display panel shown in FIG. 2 is integrated with a force or pressure touch-control function. The so-called force or pressure touch-control means that, when pressures or forces applied by a finger are different, the display panel generates different sensing signals based on different pressures to execute corresponding operational instructions.
Currently, there are two major types of force touch functions in display panels: resistive force touch and capacitive force touch. In particular, the resistive force touch is highly valued in industry due to its high sensitivity and low cost. In current resistive touch display panels, a strain gauge is disposed under a backlight layer of a display panel or is disposed around the border of the display panel.
When a strain gauge is disposed under the backlight layer of a display panel, the thickness of the display panel increases, which is not beneficial to the thinning of the display panel. Meanwhile, since the strain gauge is disposed under the backlight layer, the sensitivity of finger touch is largely weakened, thus lowering the touch-control sensitivity. When a strain gauge is disposed around the border of a display panel, since the border of the display panel is primarily affixed using double-faced adhesive tapes, there is often a gap between the double-faced adhesive tape and the display panel that reduces deformation induced by a force applied on the surface of the display panel, which can lower the accuracy of force touch.